The physiological effects of hydrostatic pressures ranging to 300 atmospheres include convulsions and reversal of anesthesia. These observations indicate that pressure can modify the functional properties of cell membranes. Although the effects of temperature, ionic strength, etc. on model membranes has been widely investigated, the effects of pressure are less understood. We propose to use modern fluorescence spectroscopic methods to investigate the effects of pressure on model membranes. A hydrostatic pressure cell with 1 kbar capabilities will be constructed. The specific measurements will be as follows: 1) Steady state and differential polarized phase fluorometry will be used to determine the rotational rates and limiting anisotropies of probes localized in the acyl side chain region of bilayers. These rates and anisotropies reflect the dynamic properties and order parameters of the membranes, respectively. 2) Wavelength-resolved phase and demodulation methods will be used to investigate the rates of dipolar relaxation around excited state fluorophores. These measurements will reveal the effects of pressure on the dynamic properties of the lipid-water interfacial region of lipid bilayers. 3) Using quenching methods which were developed in this laboratory we will investigate the effects of pressure on the partitioning of membrane-active compounds into membranes. These cmpounds will include chlorinated hydrocarbons and local anesthetics. 4) And finally, we will examine the effects of pressure on the permeabilities of membranes to ionic and non-ionic species.